The objectives of this study are: 1. To further utilize our recently developed spectro-fluorescent assay of red cell lipid peroxidation in the study of various human red cell disorders, and to assess the implications of lipid peroxidation to red cell function. 2. To explore our preliminary findings indicating a loss of red cell membrane tryptophan in response to oxidizing hemolytic agents. 3. To evaluate the active species responsible for initiating red cell membrane lipid peroxidation and tryptophan oxidation. Lipid peroxidation will be evaluated in in vitro and animal models as well as in humans with various red cell disorders including oxidant drug-induced Heinz body hemolytic anemias, thalassemia major, iron deficiency, and lead intoxication. The oxidation of cell membrane tryptophan will be assessed in similar systems with a focus on the formation of N-formylkynurenine and the quenching of red cell membrane native protein fluorescence. Potential initiators of lipid peroxidation and membrane tryptophan oxidation to be studied include singlet oxygen and superoxide anion radical.